Allan C., the song you're thinking about is called "Song For A Friend" by John Stuart.
I'll try to put it here later.
John Stuart did a few songs about his reaction to the death of JFK and was heavily involved in Bobby Kennedy's later run for the nomination. He was traveling with Bobby & I saw him with RFK in Newport, Oregon (a rally) a week before Bobby was killed in California. Bobby Kennedy lost the Oregon primary to Minnesota Senator Eugene McCarthy (NO RELATION to the infamous Joe McCarthy of House Un-American Activities infamy). I was wearing a McCarthy button at that Bobby K. rally & was challenged by a supporter of Bobby's (a mountain climber named Jack Whittaker as I recall who scaled Mount Kennedy with Bobby---that peak was named for John Kennedy) 'caus he felt Bobby was the only one who could actually win. I recall telling that fellow that I was for McCarthy because he challenged Lyndon Johnson when we needed him & that I wasn't about to abandon him now that Bobby had jumped into the race. In hindsight I see that he was probably correct.
So much for the ideals of youth...
Bobby Kennedy won the California primary a week later and it was at that victory clelebration that he was killed by Sirhan Bishara Sirhan who is still in prison for that.